Effect of Partially PurifiedStaphylococcus aureusBeta‐Haemolysin on the Mammary Gland of the Mouse

Partially purified Staphylococcus aureus Beta-haemolysin and a S. aureus strain (FGH28), isolated from a clinical case of bovine mastitis, known to produce in vitro Beta-, but neither Alpha- nor Delta-haemolysins were each injected separately into the mammary gland of mice. Relative purity and in vitro biological activities of this preparation were assessed. The effects of both the partially purified preparation and the S. aureus strain injected were assessed in terms of mortality, clinical appearance, macroscopic and microscopic changes, recovery of organisms from the inoculated glands and biological activity in supernatants from ground mammary glands. When injected alone, partially purified Beta-Haemolysin was not found to be an important virulence factor, being a diffuse infiltration of neutrophils into the alveoli the pathological effect observed following its inoculation. Vascular lesions were observed, in the most severe cases, following injection of S. aureus FGH28.